Inverse Elastic Shell Design with Contact and Friction
SessionFabulously Computed Fashion
Event Type
Technical Papers
TimeWednesday, 5 December 20184:15pm - 4:41pm
LocationHall B5(1) (5F, B Block)
DescriptionWe propose an inverse strategy for modeling thin elastic shells
physically, just from the
observation of their
geometry. Our algorithm takes as input an arbitrary target mesh,
and interprets this configuration automatically as a stable
equilibrium of a shell simulator under gravity and frictional
contact constraints with a given external object. Unknowns are the
natural shape of the shell (i.e., its shape without external forces)
and the frictional contact forces at play, while the material
properties (mass density, stiffness, friction coefficient) can be
freely chosen by the user. Such an inverse problem formulates as an
ill-posed nonlinear system subject to conical constraints. To
select and compute a plausible solution, our inverse problemsolver
proceeds in two steps. In a first step, contacts are reduced to
frictionless bilateral constraints and a natural shape is retrieved
using the adjoint method. The second step uses this result as an
initial guess and adjusts each bilateral force so that it projects
onto the admissible Coulomb friction cone, while preserving global
equilibrium. To better guide minimization towards the target, these
two steps are applied iteratively on a degressive regularization of
the shell energy.
We validate our approach on simulated examples with reference material
parameters, and show that our method still converges well for
material parameters lying within a reasonable range around the
reference, and even in the case of arbitrary meshes that are not
issued from a simulation. We finally demonstrate practical inversion
results on complex shell geometries freely modeled by an artist or automatically captured from real objects, such as posed garments or soft accessories.
physically, just from the
observation of their
geometry. Our algorithm takes as input an arbitrary target mesh,
and interprets this configuration automatically as a stable
equilibrium of a shell simulator under gravity and frictional
contact constraints with a given external object. Unknowns are the
natural shape of the shell (i.e., its shape without external forces)
and the frictional contact forces at play, while the material
properties (mass density, stiffness, friction coefficient) can be
freely chosen by the user. Such an inverse problem formulates as an
ill-posed nonlinear system subject to conical constraints. To
select and compute a plausible solution, our inverse problemsolver
proceeds in two steps. In a first step, contacts are reduced to
frictionless bilateral constraints and a natural shape is retrieved
using the adjoint method. The second step uses this result as an
initial guess and adjusts each bilateral force so that it projects
onto the admissible Coulomb friction cone, while preserving global
equilibrium. To better guide minimization towards the target, these
two steps are applied iteratively on a degressive regularization of
the shell energy.
We validate our approach on simulated examples with reference material
parameters, and show that our method still converges well for
material parameters lying within a reasonable range around the
reference, and even in the case of arbitrary meshes that are not
issued from a simulation. We finally demonstrate practical inversion
results on complex shell geometries freely modeled by an artist or automatically captured from real objects, such as posed garments or soft accessories.